Abstract
Melioidosis was first identified in Myanmar in 1911 but for the last century it has remained largely unreported there. Burkholderia pseudomallei was first isolated from the environment of Myanmar in 2016, confirming continuing endemicity. Recent genomic studies showed that B. pseudomallei originated in Australia and spread to Asia, with phylogenetic evidence of repeated reintroduction of B. pseudomallei across countries bordered by the Mekong River and the Malay Peninsula. We present the first whole-genome sequences of B. pseudomallei isolates from Myanmar: nine clinical and seven environmental isolates. We used large-scale comparative genomics to assess the genetic diversity, phylogeography and potential origins of B. pseudomallei in Myanmar. Global phylogenetics demonstrated that Myanmar isolates group in two distantly related clades that reside in a more ancestral Asian clade with high amounts of genetic diversity. The diversity of B. pseudomallei from Myanmar and divergence within our global phylogeny suggest that the original introduction of B. pseudomallei to Myanmar was not a recent event. Our study provides new insights into global patterns of B. pseudomallei dissemination, most notably the dynamic nature of movement of B. pseudomallei within densely populated Southeast Asia. The role of anthropogenic influences in both ancient and more recent dissemination of B. pseudomallei to Myanmar and elsewhere in Southeast Asia and globally requires further study.
Highlights
Melioidosis was first identified in Myanmar in 1911 but for the last century it has remained largely unreported there
Multilocus Sequence Typing (MLST) revealed that none of the STs of the clinical isolates matched the STs of the environmental isolates, with phylogenetics confirming that the environmental isolates recovered from Myanmar in this study were not closely related to the patient isolates, with > 18,000 Single-nucleotide polymorphisms (SNP)-indels separating clinical isolates from environmental isolates (Fig. 2)
Southeast Asian countries bordered by the Mekong River and the Malay Peninsula have shared genotypes and phylogenetic overlap[12]; this is likely due to the lack of geographical barriers, both as exist currently, but even more extensively during the last ice age within an expanded Sundaland (Fig. 1A)
Summary
Melioidosis was first identified in Myanmar in 1911 but for the last century it has remained largely unreported there. From Asia, B. pseudomallei subsequently spread to Madagascar and Africa and more recently from West Africa to the Americas (between 1650 and 1850), likely linked to the slave trade[12,13,14,15] This strong geographic signal of the B. pseudomallei genome is notably due to infection in humans and animals being acquired directly from an environmental source, with human–human and zoonotic transmission being exceedingly rare. Such epidemiology and large continental geographic barriers restrict gene flow and have resulted in distinct geographic populations of B. pseudomallei
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